Observations of high temperature impinging-jet boiling phenomena

A high-speed video camera and microphone were used to capture the flow behavior and boiling sound of a free-surface water jet impinging on a high temperature surface during quench cooling. It was found that depending on the superheat of the surface considerably different flow patterns appeared. For cases where the initial surface temperature was above about 300 °C an almost explosive pattern appeared. This was in contrast to slightly lower temperatures where a liquid sheet flow structure was apparent. The change in phenomena was accompanied by a sudden change in the boiling sound and an increase in the heat transfer rate.     

Statistical Criteria and Estimation Results for Regularities of Gas-Dynamic Phenomenon Distribution in Potash Deposits

An analysis and estimate are performed for possible schemes of spatial distribution of gas-dynamic phenomena in potash deposits by the methods of mathematical statistics. The problem stated is solved by comparing the numerical characteristics of the events observed and those obtained on the basis of the theoretical model developed.     

Suppression of a spontaneous dust density wave by modulation of ion streaming

Synchronization of a self-excited dust density wave has been experimentally investigated in a strongly coupled dusty plasma. A dust density wave of frequency ~78 Hz is spontaneously generated from the dust void boundary due to the ion streaming instability. The electric field in the dust void region is measured, and the electric field force and ion drag force on the dust particles at the void boundary are estimated to explain the mechanism of spontaneous dust density wave excitation. Synchronization occurring through the suppression mechanism is observed by modulating the ion streaming by applying an external sinusoidal signal to the dust void. At sufficiently high modulation amplitude, the onset of period-doubling bifurcation is observed. Fast Fourier transform spectral analysis is done using time-series data obtained from high-speed video imaging. The van der Pol equation with a force term is used to correlate the observed suppression phenomena.     

水/甲醇和柴油乳化液的黏度特性实验研究

为研究水/甲醇和柴油乳化液的流变特性与黏度,实验采用了Span80和Tween60配制的3种复合乳化剂Y01、Y02和Y03,它们的HLB值分别为5.36、4.83和4.51.Y03为牛顿流体,动力黏度约为1.5Pa·s.在高剪切速率下,Y01与Y02近似为牛顿流体,动力黏度分别为Y03的88%和92%.乳化液中水相(水与甲醇)总量为10%～50%,乳化剂含量0.8%～8%,动力黏度约在0.003Pa·s到0.02Pa·s之间,为牛顿流体.实验结果表明,如果其它条件不变,乳化液黏度变化规律为:乳化剂HLB值的不同对乳化剂黏度有较大影响;乳化剂含量对乳化液黏度有显著影响,特别当水相含量高于40%时,影响特别显著;提高水相含量(不超过50%),乳化液黏度上升,当水相含量超过40%时,乳化剂含量低于2%和高于4%对乳化液的黏度影响规律明显不同;水相中水与甲醇的比例变化时,对乳化液的黏度影响比较复杂.用乳化液相间界面特征和HLB特征可以从理论上解释上述现象.     

Chain matching between hydrocarbon and fatty acid as interfacial phenomena

According to the investigations of Cameron and his coworkers^1–5 into the chain-matching phenomena between normal paraffin as a solvent and straight-chain fatty acid as an additive, the optimum condition in boundary lubrication is attained when the chain lengths of the additive and solvent are equal. A series of experiments has been conducted over the past ten years on the role of the chain-matching effect, not only on boundary lubrication but also widely on relevant interfacial phenomena. The results of the investigations are discussed.     

Researches on Ni-P Alloys

Worldwide researches on Ni-P alloys have been briefly reviewed,including their corrosion resistance,crystallisation behaviour,amorphisation by ion implantation,and usage as underlayer for thin film magnet-ic media.     

PMSM无位置传感器控制中数字滑模观测器抖振现象分析与抑制

通过对永磁同步电机(PMSM)反电动势滑模观测器观测结果进行加窗快速傅里叶变换(FFT)频谱分析,发现抖振信号频谱范围较宽、幅值较大,观测结果无法直接使用,低通滤波器使得观测信号发生变化,难以精确补偿。本文提出了一种以电流和磁链为观测对象的扩展滑模观测器,磁链观测结果由磁链实际值和经过滤波后的抖振信号组成。根据磁链观测结果的频谱分析,抖振现象的影响可以忽略不计,转子角度可以由磁链观测结果直接计算,不需要低通滤波,避免了相位滞后。着重分析了速度估计误差对观测结果和转子角度计算的影响,并以此为基础进行反馈矩阵计算。仿真和实验结果表明该方法能够准确计算出电机的位置和速度,使系统具有良好的稳态精度和动态性能。     

Investigation of transport phenomena in a hybrid ion exchange-electrodialysis system for the removal of copper ions

Hybrid ion exchange electrodialysis processes allow the removal of metal ions from dilute waste liquids and the recovery of more concentrated solutions. The work reported here was aimed at investigating the two steps in the treatment process, namely, adsorption of metal ions onto the packed bed of resin and electromigration (i.e., the transport of these ions in the complex system under the applied electrical field). The case of copper sulfate was investigated. Dowex resins with a cross-linking degree of 2 and 8% were used. The flux of copper through the resin bed and the current efficiency for ion transfer to the cathode compartment were determined as a function of potential gradient and copper ionic fraction in the bed. Apparent diffusion coefficients of Cu²⁺ in the overall system were deduced from the experimental data.     

A DYNAMIC,ADAPTIVE, LOCALLY CONSERVATIVE,AND NONCONFORMING SOLUTION STRATEGY FOR TRANSPORT PHENOMENA IN CHEMICAL ENGINEERING

A family of discontinuous Galerkin (DG) methods are formulated and applied to chemical engineering problems. They are the four primal discontinuous Galerkin schemes for space discretization: symmetric interior penalty Galerkin, Oden-Babu?ka-Baumann DG formulation, nonsymmetric interior penalty Galerkin, and incomplete interior penalty Galerkin. Numerical examples of DG to solve typical chemical engineering problems, including a diffusion-convection-reaction system in a catalytic particle, a problem of heat transfer in a fixed bed, and flow and contaminant transport simulations in porous media, are presented. This article highlights the substantial advantages of DG on adaptive mesh modification over traditional methods. In particular, we propose and investigate the dynamic mesh modification strategy for DG guided by mathematically sound a posteriori error estimators.     

SNIPPET ON DRYING

ABSTRACT

When regarding the atmospheric contact drying of granular beds wetted with a liquid mixture, both the drying rate and the selectivity of the process, i.e. the change of moisture composition, are of interest. The batch drying of a free flowing ceramic substance, wetted with a 2-propanol-water mixture, is investigated in a rotary dryer with heated wall and air flow.

The theoretical analysis is based on physical models for heat and mass transfer, moisture migration and particle transport, which are presented in examples.

The experimental and theoretical results show that higher selectivities can be achieved by reducing the particle size because of the lower liquid-phase mass-transfer resistance. An increase of the rotational speed leads to a higher drying rate with slightly decreased selectivity if the particles are sufficiently small, since contact heat transfer is enhanced.